1. Field of the Invention
The invention generally relates to transmission and reception controls in mobile communication systems, and more particularly, to managing the operation status of wireless transmissions and receptions for the mobile terminals.
2. Description of the Related Art
For a mobile communication system, the communications between a user and the equipment (referred to as UE herein) and a service network are performed arbitrarily according to the requests from or to the user of the user equipment. Since the UE does not necessarily operate in a transmission mode or reception mode for data transmissions and receptions at all times, always keeping the UE in a transmission mode or reception mode may be unnecessary and, not to mention, is very power consuming. In order to reduce the overheads in the consumed power, the UE may employ a discontinuous reception (DRX) technique when there is no potential transmission and reception in a certain period of time. During a DRX cycle, the UE may perform wireless transmissions or receptions in a DRX-ON duration, and make the wireless module and/or other function components enter a sleep mode in a DRX-OFF duration. Specifically, when the wireless module and/or other function components in the UE are operating in sleep mode, the power consumed by the processor therein is mainly for keeping a low-rate clock for timing synchronization with the connected service network.
However, the potential transmission and reception may involve unnecessary monitoring on the downlink channel, which results in prolonging the DRX-ON duration to an extent where the UE always remains operative even if there is no data transmission or reception. Take a Long Term Evolution (LTE) system for example. As shown in FIG. 1, when a UE configured with a DRX cycle wishes to perform wireless transmission, it conventionally wakes up from sleep mode to transmit a scheduling request (referred to as SR herein) message to the connected service network and monitor the downlink channel for a response message. If there is no response message received in a waiting period TSR, the UE retransmits the SR message and monitors the downlink channel for a response message again, until a response message (denoted as UL grant message) is received from the connected service network. Note that the intervals between the transmissions of the SR message are all DRX-ON durations in which the UE remains operative for all time before a response message is received, even if the UE employs the DRX technique. FIG. 2 is a schematic diagram illustrating the conventional operation status of a UE employing DRX technique and SR prohibition control. Similar to FIG. 1, when a UE configured with a DRX cycle wishes to perform wireless transmission, it wakes up from the sleep mode to transmit an SR message to the connected service network and monitor the downlink channel for a response message. However, with the SR prohibition control employed, the retransmission of the SR message is prohibited for a predetermined number of times to avoid unnecessary SR transmissions on the uplink channel, especially for voice-over-IP (VoIP) traffic. As shown in FIG. 2, the predetermined number of prohibited SR retransmissions is set to 2. That is, the retransmission of the SR message is performed if no response message is received from the connected service network in 3 times of the waiting periods TSR (i.e. plus 2 additional waiting periods for the prohibited SR retransmissions). Note that even if the SR prohibition control is employed, the UE still has to remain operative during the waiting periods for the prohibited SR retransmissions. Thus, the DRX-ON duration is unnecessarily prolonged in the conventional design, which contradicts to the intention of the DRX technique and causes significant overheads in power consumption.